Java 如何在springboot的ConversionService中自动连接

试图访问springboot中模型中的ConversionControl，运气不佳

@Component
public class CityHelperService  {

    @Autowired
    ConversionService conversionService;// = ConversionServiceFactory.registerConverters();

    public City toEntity(CityDTO dto){
        City entity = conversionService.convert(dto, City.class);
        return entity;
    }

    public CityDTO toDTO(City entity){
        CityDTO dto = conversionService.convert(entity, CityDTO.class);
        return dto;
    }
}

它显示以下错误：

Injection of autowired dependencies failed;
nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: com.lumiin.mytalk.model.CityModel com.lumiin.mytalk.controllers.CityController.cityModel;
nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'cityModel' defined in file : Unsatisfied dependency expressed through constructor argument with index 1 of type [com.lumiin.mytalk.dao.CityHelperService]: : Error creating bean with name 'cityHelperService': Injection of autowired dependencies failed;
nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: org.springframework.core.convert.ConversionService com.lumiin.mytalk.dao.CityHelperService.conversionService;
nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.springframework.core.convert.ConversionService] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)};
nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'cityHelperService': Injection of autowired dependencies failed;
nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: org.springframework.core.convert.ConversionService com.lumiin.mytalk.dao.CityHelperService.conversionService;
nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.springframework.core.convert.ConversionService] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}

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从最后一个嵌套异常判断，显然没有可用的

ConversionService

bean：

org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.springframework.core.convert.ConversionService] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency.

查看后发现，您应该声明一个

ConversionService

bean。在XML配置中，它将如下所示：

<bean id="conversionService" class="org.springframework.context.support.ConversionServiceFactoryBean">
    <property name="converters">
        <set>
            <bean class="example.MyCustomConverter"/>
        </set>
    </property>
</bean>

---

不完全同意接受的答案，因为将有一个名为

mvcConversionService

的默认

ConversationService

，因此您将得到重复bean异常。相反，将Converter添加到

FormatterRegistry

，以下是部分答案的链接：

您还需要（在某些情况下）为

转换服务

定义至少一个空的

组件

，如下所示：

@Component @Primary
public class MyConversionService extends DefaultConversionService implements ConversionService {
    // an empty ConversionService to initiate call to register converters
}

这将强制spring容器启动对以下对象的调用：

class WebMvcConfigurerAdapter {
    ...

    public void addFormatters(FormatterRegistry registry) {
         //registry.addConverter(...);
    }
}

---

谢谢你的评论。但是什么是bean.setConverters（…）；它显示了一个错误-org.springframework.core.convert.ConverterNotFoundException:找不到能够从com.lumiin.mytalk.dto.CityDTO类型转换为com.lumiin.mytalk.model.CityYou可能没有指定转换器-您必须创建一个类，该类实现接口

转换器

，另一个反过来，然后在

转换服务工厂bean

中注册这两个。请看本教程：在Javaconfig中，您甚至不需要像上面的示例那样从

ConversionServiceFactoryBean

返回

ConversationService

，只需返回一个

ConversionServiceFactoryBean

bean，spring将为您完成其余的工作

mvcConversionService

仅当您的项目中有

org.springframework.boot:spring boot starter web

依赖项时才会出现

class WebMvcConfigurerAdapter {
    ...

    public void addFormatters(FormatterRegistry registry) {
         //registry.addConverter(...);
    }
}